Summary - (Aug 9, 2005) Our planet gained its nice, oxygen-rich
atmosphere about 2.4 billion years ago thanks to early bacteria. One
question that has puzzled researchers, however, is why it took at least
300 million years for oxygen to build up to large levels, even though
the bacteria had been working madly to produce it. Researchers from the
University of Washington have developed a model that shows how volcanic
gasses could have sucked up this available oxygen. Not only that, but a
large layer of iron from meteorite strikes would have used it for
rusting. Not until those sinks were filled could oxygen build up.


See http://tinyurl.com/a7ero for more

Maybe I'm stupid but I have a real big problem with what is discussed
herein. ...

Nitrogen. It makes up most of our atmosphere. Why ?



RL